Although i have Outlook installed and set as Default mail app, it's not showing up as an option in the Contacts Manager, for some reason. I had exported/imported my contacts to the official Contacts app so at the moment I have all contacts locally. But I realize this means that if I add a new entry within Outlook, the new person won't be an option for phone/text. Any ideas?
I had this happen to me, when I was moving my daughter to Android (we were all on Windows, for years, as a ex-Win engineer).
As such, I'm sort of married to the Win AD model for most stuff, and Outlook, accordingly, it just works for me, I understand the security well, etc. I also expect the syncs to be a normal part of the functionality, as you're looking for.
Anyway, I fiddled, and fiddled, and I'm sure my head spun around a few times, it just wouldn't pick up on the fact I'd designated Outlook as my source.
Eventually, since it was a new phone anyway, I did a reset, re-installed Outlook (obviously), and all of sudden the "Outlook souce" for contacts was "just there".
If I were you, and not wanting to do a factory reset (to start anyway), I'd nuke all my current contacts (assuming they live in the Live cloud space anyway), un-install and re-install Outlook, and I bet the source for Outlook Contacts will just appear.
My experience (above) was on a ZTE Axon, the one where it was maddening, maybe 9-10 months back.
When I moved, about 1.5 years ago, to a 6P, I had zero issues getting this to work. Recently, I moved to a 5T, which was a huge pain, because I was running 8.0.1 on my 6P, and the 5T had 7.1, and Android is woefully "short" in this area, they don't support any sort of "partial downgrade" to "close versions.
As such, I had to re-install, after backing up some stuff, like text/call history with tools, and rebuild most of the 5T from scratch (oh well, it runs well, such is life), and the import all the stuff I wanted.
I had a bit of frustrating experience, again with contacts not recognizing Outlook as a source, but un-installed and re-installed, fiddled with something (trying to recall...), and zip, it "just worked".
Personally, from a s/w engineering perspective, I think there's a bug in the Contacts setup mechanism somewhere, when you're trying to use things other than G-Cloud, as a source. I'm not motivated enough to fire up a debugger though, and even if I did report it, I'm not sure how motivated Google would be, to fix it (since it mostly works, sorta).
I bet Samsung has added some more of their "cloud presence" to the Android variant too, they seem to think that you "must" want to move to theirs, vs. the standard Live/Google/whatever cloud mechanism that you're all established in, IME.
Samsung makes great hardware, but I'm not a big fan of their s/w mods, or their desire to try and force you into "their space" for a lot of things, the "Bixby button" is another example...
Good luck, hopefully this is hopeful, and not just a diatribe...